Spark-plug



M. B. JACOBSON.

SPARK PLUG.

Patented Mar. 15, 1921.

/H HH UNITED STATES PATENT OFFICE.

MARTIN B. J'ACOBSON, OF BLAIR, NEBRASKA.

SPARK-PLUG.

To all whom it may concern:

Be it known that I, MARTIN B. J ACOBSON, a citizen of the United States of America, residing at Blair, in the county of Washington and State of Nebraska, have invented certain new and useful Improvements in Spark-Plugs, of which the following is a specification.

My invention relates to electric spark igniting devices, for internal combustion engines in which electrodes are permanently separated in the combustion chamber of the engine to produce a jump-spark by a current of electricity of high electromotive force, and among the most importantobjects of my invention are:

First. To shape and dispose the electrodes so as to form a spark gap'of the greatest possible width within a limited area and at the same time conserve a uniform length of gap throughout such width; it being understood that the length of the gap is the distance or space between the two electrodes and the width is the distance at right angles thereto throughout the uniform space or gap; although such gap may be, as intended and curved in this case, much wider than the length'thereof. f Second. To facilitate the use of mica insulation in both high pressure and low presof the electrodes against warping and char-.

ring by the effects of intense heat, but to place them in such relative positions as to brin the plane of a wide curved gap where it W111 be least varied by such warping as is unavoidable, or by mechanical disturbances in assembling, adjusting or transporting and marketing the completed spark plugs.

Fifth. To produce a spark plug adapted to be used in either high or low pressure cylinders without change of structure or adjustment the explosion chamber of an engine.

Specification of Letters Patent. Patented M 15 1921 Application filed May 13, 1919. Serial No. 296,857.

the mouth of the seating shell; and Fig. 2, an inner end or lower end view, being the electrode or sparking end of the plug.

The power electrode consists of the disk 3, WhlOh is an axially disposed integral terminal part of its supporting conductor rod 4. The conductor rod 4 is seated axially through the insulating plug or core 5 and has its end opposite to the disk threaded to receive fastening nuts; also with the terminal nut to serve as a binding post for connection; with the power current line in the usual manner, as will be readily understood by observing Fig. 1. The insulation core is in a like usual manner concentrically seated in the outer end of the exteriorly threaded seating-shell 6, by which the plug is inserted through the. walls of and ilnltlo e conductor rod is adjusted endwise to bring the sparking face of its terminal disk elecf'lrode substantially in a plane agreeing with the inner end or rim 14 of the shell 6. In this position the disk occupies a central concentric portion of the mouth of a chamber 13 between the disk and the inner end of the insulation core 5 and within the inner end of the shell. This shapes said mouth to the form of an annular space 15 between the periphery of-the disk electrode and the inner rim of the shell, and reduces the area of cross section of the mouth to much less than that of the chamber 13 surrounding the rod above the disk electrode.

The ground electrode consists of a single piece of wire, of any desired metal. A central portion of the wire is bent. to form the are 7 of curvature substantially agreeing with the periphery of the disk electrode and subtending nearly a complete circle, as shown in Fig. 2. Adjacent to the ends of this) central arcuate looped section, the reverse bonds 11 and 11 are made to dispose the supporting leg portions 8 and 8 standing divergently outward to broaden the foothold or base-space between the attaching feet 9 and 9. These foot ends 9 and 9 are bent to stand upwardly at right angles to the plane of the arcuate section, reversely curved bends and outwardly divergent supporting legs; and are seated and fastened in longitudinal perforations in the rim 14 of the shell, tosupport the arcuate section in a plane parallel with but spaced axially away from the face of the disk electrode. This forms the spark gap 10 extending in curved width nearly the whole circumferential distance around the edge of the face of the disk electrode and in longitudinal spacing therefrom. The reverse curve bends 15 lying in the same plane as the arcuate central section, the opposite terminal or side edges of the gap occur between these bends and the angle edge 12 of the discal electrode above; the reversely curved bends being spaced apart a greater distance than the length of the spark gap. I

Starting by the use of a new plug, w1th ordinary conditions of construction and the electrodes reasonably clean, the first sparks occur at one or the other of the two points where the reverse c'urves 11 and 11 cross outwardly under the angle 12 at the outer ed e of the face of the discalelectrode: the si e edges of the spark gap. As the changing conditions, of temperature, fouling by soot or oil and changes wrought in the char acter of the metal, by use and age, take place, the point of occurrence of spark shifts about in the width of the gap, obviously always jumping at the place of least resistance. This constant irregular shifting of the point of sparking throughout the great width of the gap and around the outer edge of the .discal electrode results in advantages as follows:

The open looping curvature of the ground electrode leaves a large central field of the face of the discal electrode unobstructed, so that explosion of the fuel mixture occurs within this ring as quickly as around the outer or opposite side of the gap. The oft changing of position of initial ignition around this circle, changing the direction of the start of ex losion, has a scouring cffeet that keeps t e face of the disk clean.

Simultaneously a scouring effect on the inner surface of the curved wire electrode results from this shifting about of the point break up and loosen incrustations that may for theuse of mica washer insulation cores form thereon. The scouring action on the sparking lines of the electrodes is further facilitated as follows:

The discal electrode as placed shapes the annular strictured mouth 15 to lie around '70 outside of and adjacent to the curved spark gap and curved edges or spark lines of the electrodes. As the pressure is varied in the explosion chamber of the engine: by the return stroke of its piston, the release of pressure by the exhaust and the force of the explosion of the fuel mixture, there is produced rapid forceful alternately back and forth currents of gases and fuel mixture. through this mouth; caused by the normal tendency of the contents to assume an equal pressure throughout the connected chambers. These forceful vibratory currents through the mouth have an efficient abrading action on the peripheral surfaces of the electrodes.

The disposition of the electrodes as above set forth, and shown in the drawing, whereby all are well retired within or close to the chamber of the shell, avoiding isolated and far projecting parts in the explosion chamber, in connection with the cooling effects of the alternating gas and fuel currents through the surrounding mouth, prevents the electrodes from becoming superheated to the extent of causing preignition of the fuel mixture. This adapts this spark plug to effective use in high pressure fuelmixture-chamber engines, as well as in those of ordinary low pressure, without change of structure or adjustment.

It is. obvious that the broad power electrode as arranged to'stricture the mouth of the chamber in the shell, to a great extent shields the well retired inner end and body of the insulator core 5; thereby preventin it from being coated with lubricating oi thrown into the explosion chamber b the engine piston; thereby adapting the evice for engines of high pressure ignition chambers. That the opposite halves of the wire ground electrode each consists entirely of bends of the Wire made in an opposite direction to that of the other half and equal reverse bends in likejreverse positions in opposite halves; bythis means any tendency of the heatin to correct the set in the metal wire, caused y the bending in shaping the electrode, is exactly balanced in the opposite halves of the electrode and it therefore And the does not lose its shape in use.

curved arcuate or looped portion 7, doubtless least apt to be distorted at .its center or vertex, where least sparking occurs, lies as an integral rigidly connecting brace between the opposite halves and at t point farthest removed from the rigidly seated feet. Further, the broad-spaced base of attachment, the feet 9 and 9 and angularly disposed legs 130 8 and 8, makes certain the connection and security of attachment and braces the ground electrode against any tendency to lateral displacement. As shown, the divergent legs 8 and 8, the only and short portions of the wire that are not bent in shaping the electrode, are disposed across the annular strictured mouth 15 of the shell chamber 13, where they are constantly cooled by the alternating fuel and air and gas mixture currents passing therethrough. i That, any warping of the power electrode supporting rod, or turning or shifting it in its insulatory support, has little effect on the discal electrode, other than to move it edgewise in its set discal plane, not materially modifying the uniform length of the gap at any point throughout its circular width.

I claim:

In a spark plug, a tubular seating shell, a tubular insulating core seated axially in said shell with its inner end spaced outwardly from the inner end of the seating shell, a conductor rod disposed axially through said insulating core, a discal electrode of less diameter than the bore of said shell disposed concentrically on the inner end of the conductor rod and flush with the inner rim of said seating shell to partly inclose a chamber therein and form an annular mouth open inwardly from said chamher, in combination with an opposed ringshaped electrode of diameter substantially equal to said discal electrode and spaced inwardly from the edge thereof to form a spark gap of less length than the width of said annular mouth and of Width nearly equal to the whole circumference of said discal electrode, said ring electrode divided at one side by a space only a little wider than the length of said spark gap, and integral supporting legs disposed divergently from the ring at opposite sides of said space and having outwardly-angled feet seated in the rim of the seating shell.

In testimony whereof I hereunto afiix my signature.

MARTIN B. JACOBSON. 

